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ARP 8740 or 2000 rod bolts

Old 07-05-2016, 09:24 PM
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Default ARP 8740 or 2000 rod bolts

Alright I just purchased some ebay rods for my build that came with ARP hardware. They listed in the ad that they would include ARP 8740 bolts unless you specified for others(at additional charge). I did request that they upgrade to ARP2000 as that seems to be the common one to use now(newer metallurgy from what I have found). Well they came in today but looking at my account they didnt charge for the arp2000 and sent the 8740. From what I understand it is still a good material, but not quite up to the specs of the 2000s.

Should I contact them and get a set of ARP2000s or are the 8740s reliable for my build(05 engine that will be N/A and rev limited to no more than 7500 rpm and eventually be boosted but staying under 275whp) I think the rpm will be the real limiting factor in this but I havent seen anything miata specific between the two materials, only LS and Mustang reviews and the BP has some pretty bad rod ratios that would load the bolts a bit more heavily so I'm a bit concerned about that.

Anyone have experience with these different bolts here?
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Old 07-06-2016, 12:14 AM
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Miatas also have crappy rod ratios.

I've never heard of 8740. Pretty much every set of proper rods I've seen comes with ARP2000 bolts.
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Old 07-06-2016, 10:01 AM
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Yes, that is what I said slightly concerns me is that the miata/BP engine has pretty bad rod ratios so it increases rod bolt load pretty heavilly.

Yes, now all the reputable vendors include ARP2000 but those are newer so from what I can tell 8740 was the standard before the ARP2000 came out. The 8740 is already much stronger than than OEM the tensile ratings for the different materials seem to be as follows
OEM 160-170kpsi,
8740 190-210kpsi(depending on heat treatment)
ARP2000(material is 1722) 220kpsi

So you can see how close the 8740 is to the ARP2000 so I really think I should be fine as my rpm should not be too high and it is a street car so it will not see sustained high rpm anyway. I just want to make sure I got all this back together and it won't come apart on me.

Originally Posted by AlwaysBroken View Post
Miatas also have crappy rod ratios.

I've never heard of 8740. Pretty much every set of proper rods I've seen comes with ARP2000 bolts.
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Old 07-06-2016, 11:18 AM
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I highly doubt you will have any issues with them. I would run them and not think twice about it.
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Old 07-06-2016, 01:54 PM
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Thats what I want to hear. I was leaning that way just wanted to make sure I wasnt missing something
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